The present invention relates to medical devices, and more particularly, to an improved multiple dose infusion controller for delivering multiple doses of intravenous drugs at selected intervals at a controlled rate to a patient.
There is an ever increasing desire in the health care field to get patients out of expensive hospital care environments and back to their homes. Many such patients require intravenously administered medications, but are unable to afford the expensive equipment necessary to administer the medication in the prescribed manner.
It is often necessary to intravenously supply patients with multiple doses of pharmaceutically active liquids over a long period of time at a controlled rate. It is desirable that this be accomplished while the patient is in an ambulatory state. It is also desirable that the infusion system incorporate means for keeping the veins of the patient open between periods of infusion.
The prior art includes devices that employ a bag filled with fluid medication that feeds by gravity through IV tubing having drip or other controllers. It is difficult for a patient to be ambulatory with a gravity fed infusion device. In addition, flow control in this type of device is typically manual and very limited.
Another prior art infusion apparatus comprises an elastic bladder forming a liquid container, an elongated cylindrical housing enclosing the bladder, a flow control valve, and tubing for supply of the liquid to the patient. The elastic walls of the bladder expand along the walls of the cylindrical housing when filled with the liquid, and provide the pressure for expelling the liquid. While such devices are suitable for ambulatory use, the flow control is usually manually operated valves or clips and very limited.
Attempts have been made to control pressure and flow rates in many of these devices by means of complicated and expensive flow control valves and devices. Other approaches have utilized exotic and expensive elastic materials in an effort to control the pressures and flow rates.
Another type of infusion apparatus uses pressurized gas as the driving force for the intravenous liquid. In such systems, there may be hydraulic feedback through the pneumatic source in order to precisely regulate hydraulic pressure. See for example U.S. Pat. Nos. 4,430,078 of Sprague, 4,335,835 of Beigler et al., and 4,327,724 of Birk et al.
Still another type of infusion apparatus employs a peristaltic or other positive displacement pump which is electrically driven. Programmable infusion pumps have been provided having the capability for precise tailoring of the fluid delivery rate parameters in different modes, such as continuous, intermittent, PCA (patient controlled analgesic) and TPN (total parenteral nutrition). Originally, such programmable infusion pumps were large and not well suited for ambulatory patients. They used complex and expensive replacement pump cartridges to maintain sterility.
More recently, small programmable infusion pumps have been available with disposable plastic cartridges that engage a peristaltic pump. However, a major drawback of existing programmable infusion systems of this type is that they are complicated and very expensive to manufacture and to maintain.
A recently developed inflatable bladder infusion device has many desirable characteristics for inexpensive ambulatory use. The device has a highly uniform pressure and flow rate and is inexpensive to manufacture and use. However, it lacks the necessary control to provide multiple dosages with means to keep the vein open.
Accordingly, it would be desirable to provide an improved low cost multiple dose controller for use with inexpensive infusion systems for delivering intravenous drugs in selected multiple doses at a controlled rate to an ambulatory patient that can be more easily programmed by a patient, and which will allow patient verification of the prescribed delivery parameters.